Atomic emission spectroscopy is an analytical method which is used for determining and measuring the chemical composition of materials. According to this method, a material sample is heated and vaporized by a spectral excitation source. Atoms of the sample are excited and partially ionized, causing them to emit light in the ultraviolet, visible, or near infrared spectral region. The radiated light is characterized by an arrangement of spectral lines, and the intensity of these spectral lines indicates the atomic concentration within the sample.
Atomic emission spectroscopy has been used to determine material composition during steel making, since the physical properties of a metal, such as strength, hardness, and corrosion resistance, depend in part on its composition. Improving production efficiency has been difficult because analysis of the chemical composition of molten metal within a furnace has not been rapid and accurate enough to change the production process of the melt being analyzed. Furthermore, the hot, dirty environment of a furnace limits the type of apparatus that can be used in close proximity for sampling and testing to detect the presence of the constituent elements.
There have been several different methods used to determine the composition of molten metal within a furnace. Certain prior art devices pump molten metal to a remote analytical laboratory. This configuration obviates the need for environmentally protecting the sophisticated optical instrumentation, but results in very long analysis times and high construction costs. Other devices obtain samples from near the melt surface, where the slag layer can interfere with the analysis. Yet other devices utilize a probe inserted into the melt to excite a small portion of the molten metal while still in the furnace. While such a method avoids costs associated with sampling, high development and materials costs are required to position and operate optical instrumentation within the probe in such an extreme temperature environment.